CATV networks supply and distribute high frequency “downstream” signals from a main signal distribution facility, known as a “headend,” to premises (e.g., homes and offices) of subscribers. The downstream signals can be provided to subscriber equipment, such as televisions, telephones, and computers. In addition, most CATV networks also receive “upstream” signals from subscriber equipment back to the headend of the CATV network. For example, a set top box can send an upstream signal including information for selecting programs for viewing on a television. Also, upstream and downstream signals are used by personal computers connected through the CATV infrastructure to the Internet. Further, voice over Internet protocol (VOIP) telephones use upstream and downstream signals to communicate telephone conversations.
To permit simultaneous communication of upstream and downstream signals, and to permit interoperability of subscriber equipment and equipment associated with the CATV network infrastructure, the downstream and upstream signals are confined to two different frequency bands. For example, in CATV networks, the downstream frequency band can be within a range of about 54 to 1002 megahertz (MHz) and the upstream frequency band can be within a range of about 5 to 42 MHz.
Downstream signals can be delivered from infrastructure of the CATV network to the subscriber premises via a network interface device (which may also be referred to as an entry device, an entry adapter, a terminal adapter, or a drop amplifier). A network interface device can be a multi-port device, in which an upstream entry port connects to a drop cable from the infrastructure of the CATV network, and one or more input/output ports (hereinafter “ports”) connect to subscriber equipment distributed around a premises of a subscriber.
The network interface device can include two paths: an active signal communication path and a passive signal communication path. The active signal communication path can include active components (e.g., powered devices) that amplify and/or condition downstream signals received from the CATV infrastructure and conduct them to one or more ports of the CATV entry adapter. Subscriber equipment connected to these active ports benefit from this amplification of the CATV downstream signal. However, the loss of power to the entry adapter prevents communication of active CATV signals by the active components. Additionally, one or more of the ports can be connected to the passive signal communication path, which lacks any active components. As such, subscriber equipment connected to these passive ports can operate in the event of power loss. For example, the passive signal communication path may be used to provide a “lifeline telephone service” that remains operative when a subscriber premises losses power.